Natural suede leather is traditionally made by buffing the surface of a leather, usually the under or flesh side, with a carborundum or emery wheel to separate the natural fibers comprising the leather into a fine nap to provide a soft, luxurious, appealing, velvet-like surface. Fine suedes have a characteristic, multi-toned or subtly mottled appearance which is visibly altered when the fingers are traced across the surface ("finger-tracking effect"). The tactility and appearance of suede leather results from the multiplicity of fibrils raised on its surface, the fibrils being fine enough to respond readily to the touch and remain somewhat displaced laterally when the fibrils are moved, but having sufficient stiffness and resilience to retain the napped character of the surface.
Efforts have long been made to produce suede-like fabrics which simulate suede leathers. Particularly desired have been fabrics with subdenier surface fibers, i.e. surface fibers having a linear density of less than 1 denier per filament (less than 0.11 tex per filament). The term "suede-like" as used herein, is intended to comprehend fabrics having at least one raised nap surface comprised of closely-spaced fibers of low linear density and characterized by a soft, luxurious hand, regardless of basis weight of the fabrics. One commercial method for making such fabrics has involved preparing a woven or knitted fabric of wool, cotton, or one of the synthetic fibers, followed by napping of one or both fabric surfaces and shearing of the nap. Among the disadvantages of these fabrics has been insufficient fineness of the nap. Another commercial method has involved electrostatic deposition of fine flock fibers upon a fabric coated with adhesive. Although such flocked fabrics can be made with a suede-like surface comprised of somewhat finer fibers than the napped fabrics, they lack the luxurious tactility of suede leathers. In addition to commercially known products, other suede-like products are disclosed by the prior art. Evans, for instance, discloses in Example 57 of his U.S. Pat. No. 3,485,706 subjecting a polyethylene film-fibril sheet of continuous plexifilamentary strands to high-energy-flux streams of water to make a product having a suede-like texture; however, the fabric so prepared is limp or "dead" and has a waxy hand lacking in luxurious tactility.
Another approach to the problem of creating suede-like fabrics is described in British Pat. No. 1,300,268 wherein special composite fibers, designating as "islands-in-a-sea" fibers and comprising a plurality of superfine filamentary constituents (island component) in a matrix of a different constituent (sea component) are extruded and a fabric is prepared from the fibers, after which a pile of the fibers is formed on the surface of the fabric. The matrix of the composite fibers is then leached away, leaving a pile of superfine fibers. Finally, the fabric is impregnated with polyurethane and buffed. A disadvantage of this composite fiber is that the sea constituent is not utilized in the end use of the fiber resulting in a high cost for the end product. An analogous product, described by Nishida et al. in U.S. Pat. No. 4,073,988, is also based on the use of a special composite fiber, which can be split into numerous filamentary constituents by solvents having a swelling action upon the fiber. The fibers are knit into fabric form and a nap is raised before they are split; and the fabric having a nap of superfine filaments is then impregnated in turn with a water soluble polymer and a polyurethane, after which it is buffed. Another such product, described by Hayashi et al. in U.S. Pat. No. 4,051,287, relies on a hollow composite fiber which divides into numerous very fine fibrils. While such products closely resemble suede leather, each has limitations and they all involve complex and expensive processes. Accordingly, a need has been felt for a more versatile suede-like fabric which can be made by a simpler manufacturing process.